To provide a lens device with a defogging function capable of preventing the inside of a lens barrel 2 from becoming foggy even if gas is generated from an adhesive 30.

The lens device 1 stores, in a lens barrel body 2, a lens group 4 comprising a plurality of lenses including a joined lens 21 joined on an optical face, and is formed with a cutout communicating with a space surrounded by the joined lens 21, the lens 22 built separately at a front or rear side thereof, and the lens barrel body 2 with the outside of the lens barrel body 2 at an outer circumferential edge of at least one of the joined lens 21 or the lens 22. Air can thereby flow between the inside of the lens barrel body 2 and the outside thereof, and the inside of the lens barrel 2 is prevented from becoming foggy even if the gas is generated from the adhesive 30.